Modified ion exchange resin, preparation method and application of modified ion exchange resin in treatment of shale gas wastewater

Abstract

The invention relates to the technical field of wastewater treatment, in particular to modified cation exchange resin, a preparation method and application of the modified cation exchange resin in shale gas wastewater treatment. The modified cation exchange resin is characterized in that the modified cation exchange resin is obtained by compounding cation exchange resin and sodium alginate and then grafting N, N-dimethylacrylamide, and the surface of the modified cation exchange resin has an amido group; wherein the cation exchange resin is weakly acidic cation exchange resin taking carboxylic acid groups as exchange groups. The modified cation exchange resin provided by the invention simultaneously contains carboxyl, hydroxyl and amido, can simultaneously adsorb organic pollutants and metal ions through various mechanisms (such as ion exchange, hydrogen-bond interaction, chelation, hydrophobic interaction and the like), and remarkably improves the treatment capacity and efficiency of the resin on complex wastewater. In addition, the dispersibility of the modified resin in water is improved due to the hydrophilicity of the modified resin, so that the modified resin shows higher stability and efficiency in the treatment process.

Description

Technical Field

[0001] The invention relates to the technical field of wastewater treatment, and in particular to a modified cation exchange resin, a preparation method and application thereof in treating shale gas wastewater. Background Art

[0002] The membrane concentrate of shale gas wastewater is a high-concentration liquid produced after shale gas wastewater is treated by membrane. Its characteristics are more prominent and the treatment is more difficult. The characteristics of this concentrate are mainly manifested in the following aspects: First, the salt content is extremely high, usually 3 to 5 times that of the original shale gas wastewater, or even higher, and the salinity may exceed 300,000 mg / L, far exceeding the salinity of seawater. This extremely high salinity makes it difficult to deal with conventional treatment methods, greatly increasing the difficulty of treatment. Secondly, the organic matter content in the concentrate is also significantly increased, and the chemical oxygen demand (COD) may be as high as tens of thousands of mg / L. These organic substances not only increase the difficulty of treatment, but also may cause secondary pollution. Third, heavy metal elements such as barium, strontium, lead, arsenic, etc. are also enriched during the concentration process, and their concentrations may reach several times or even dozens of times that of the original wastewater. The toxicity and bioaccumulation of these heavy metal elements greatly increase the environmental risks of the concentrate. Fourth, the concentrate also contains a variety of complex organic compounds, including polycyclic aromatic hydrocarbons, phenols, organic acids, etc. These substances are not only difficult to degrade, but may also cause long-term harm to the environment and human health. Fifth, the pH value of the concentrate is usually strongly acidic, which further increases its corrosiveness and difficulty in handling. In addition, the concentrate may also contain residues of various additives, such as friction reducers and fungicides used in fracturing fluids. The presence of these substances makes the composition of the concentrate more complex and further increases the difficulty of handling.

[0003] At present, the treatment of shale gas wastewater membrane concentrate still faces many shortcomings and difficulties. First, traditional physical and chemical treatment methods such as precipitation and filtration are almost ineffective for such high-salinity concentrates, and it is difficult to achieve effective pollutant removal. Secondly, due to the extremely high salt and organic content in the concentrate, the microbial activity of the biological treatment method is severely inhibited, and the treatment effect is extremely poor. Thirdly, although the evaporation crystallization method can achieve "zero discharge" of the concentrate, it has extremely high energy consumption and huge costs, and the solid waste generated is difficult to treat and may cause secondary pollution. Membrane treatment technology performs well in treating raw shale gas wastewater, but in the face of highly concentrated concentrates, membrane pollution and scaling problems are more serious, the membrane life is greatly shortened, and the operating cost soars. In addition, the removal of heavy metal elements in the concentrate is also a huge challenge. Conventional heavy metal removal methods such as chemical precipitation have extremely poor effects in such a high-salinity environment and are difficult to meet emission standards. Summary of the invention

[0004] To solve the problems in the background technology, the present invention provides a modified cation exchange resin, a preparation method and an application thereof in treating shale gas wastewater.

[0005] To achieve the above object, the first technical solution adopted by the present invention is: The modified cation exchange resin is obtained by compounding a cation exchange resin with sodium alginate and then grafting N,N-dimethylacrylamide, and has an amide group on the surface; wherein the cation exchange resin is a weakly acidic cation exchange resin with a carboxylic acid group as an exchange group.

[0006] Preferably, the mass ratio of the cation exchange resin to the sodium alginate is 1:(0.3-0.8), and the mass ratio of the N,N-dimethylacrylamide to the cation exchange resin and the sodium alginate composite material is (0.5-2.0):1.

[0007] Preferably, the concentration of the sodium alginate solution is 1.5-2.5% w / v.

[0008] The second technical solution adopted by the present invention is: The preparation method of the modified cation exchange resin comprises the following steps: After the fully dispersed cation exchange resin solution and the sodium alginate solution are uniformly mixed at room temperature, a calcium chloride solution is added for cross-linking, and the cross-linked product is washed and dried to obtain a composite material; In a nitrogen atmosphere, potassium persulfate is used as an initiator, N,N-dimethylacrylamide monomer is added to the composite material to react at 50-60° C. for 6-8 hours, and the reaction product is washed and dried; The cation exchange resin is a weakly acidic cation exchange resin with carboxylic acid groups as exchange groups.

[0009] Preferably, the mass ratio of the initiator, N,N-dimethylacrylamide monomer and the composite material is (0.01-0.05):(0.5-2.0):1.

[0010] Preferably, the concentration of the calcium chloride solution is 3-7% w / v.

[0011] Preferably, the cross-linked product is washed with deionized water and then dried at 60-80° C. for 12-24 hours to obtain the composite material.

[0012] Preferably, the reaction product is washed alternately with deionized water and ethanol and then vacuum dried at 60-80° C. for 24-36 h.

[0013] The third technical solution adopted by the present invention is: The shale gas wastewater membrane concentrate treating agent contains the modified cation exchange resin of the first technical solution, or the modified cation exchange resin obtained by the second technical solution.

[0014] Preferably, the method is composed of the following raw materials in parts by weight: 10-20 parts of modified cation exchange resin, 5-15 parts of potassium permanganate, 10-20 parts of aminomethylated wattle bark tannin, 5-15 parts of sodium carbonate, and 15-25 parts of activated carbon.

[0015] Preferably, the preparation method of the aminomethylated wattle bark tannin is: Dissolve the tannin from the bark of thorn tree in deionized water and adjust the pH value of the solution to 8.5-9.0. Add formaldehyde solution and diethylamine, mix well and react at 70-80°C for 3-5 hours. After the reaction is completed, cool to room temperature. Adjust the pH value of the reaction solution to 3.0-4.0, add ethanol for precipitation, filter, collect the precipitate, wash and dry.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. The modified cation exchange resin provided by the present invention contains carboxyl, hydroxyl and amide groups at the same time, and can simultaneously adsorb organic pollutants and metal ions through various mechanisms (such as ion exchange, hydrogen bonding, chelation, hydrophobicity, etc.), significantly improving the resin's ability and efficiency in treating complex wastewater. In addition, the hydrophilicity of the modified resin improves its dispersibility in water, making it show higher stability and efficiency during the treatment process.

[0017] 2. The present invention uses modified cation exchange resin as a shale gas wastewater membrane concentrate treatment agent, which can achieve efficient removal of organic pollutants and metal ions in shale gas wastewater membrane concentrate.

[0018] 3. The present invention combines the selective ion exchange function of the modified cation exchange resin with the strong oxidizing property of potassium permanganate, the adsorption and complexing ability of aminomethylated wattle bark tannin, and the extensive adsorption characteristics of activated carbon to form a multiple decontamination mechanism, thereby ensuring the stability and reliability of the treatment process, and maintaining excellent treatment effects even in the face of shale gas wastewater membrane concentrate with complex components and fluctuating concentrations. DETAILED DESCRIPTION

[0019] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] The first embodiment of the present invention provides a modified cation exchange resin, which is obtained by compounding a cation exchange resin with sodium alginate and then grafting N,N-dimethylacrylamide, and has amide groups on the surface; wherein the cation exchange resin is a weakly acidic cation exchange resin with carboxylic acid groups as exchange groups.

[0021] In some preferred embodiments, the mass ratio of the cation exchange resin to the sodium alginate is 1:(0.3-0.8), and the mass ratio of the N,N-dimethylacrylamide to the cation exchange resin and the sodium alginate composite material is (0.5-2.0):1.

[0022] In some preferred embodiments, the concentration of the sodium alginate solution is 1.5-2.5% w / v.

[0023] The second embodiment of the present invention provides a method for preparing a modified cation exchange resin, comprising the following steps: After the fully dispersed cation exchange resin solution and the sodium alginate solution are uniformly mixed at room temperature, a calcium chloride solution is added for cross-linking, and the cross-linked product is washed and dried to obtain a composite material; In a nitrogen atmosphere, potassium persulfate is used as an initiator, N,N-dimethylacrylamide monomer is added to the composite material to react at 50-60° C. for 6-8 hours, and the reaction product is washed and dried; The cation exchange resin is a weakly acidic cation exchange resin with carboxylic acid groups as exchange groups.

[0024] The preparation mechanism of the modified cation exchange resin in the embodiment of the present invention is as follows: first, the weakly acidic cation exchange resin is mixed with a sodium alginate solution, and the sodium alginate molecules penetrate into the surface and pores of the resin. Subsequently, a calcium chloride solution is added, and the calcium ions (Ca² + ) and the carboxyl group (-COO - ) undergoes ion exchange reaction to form an insoluble calcium alginate gel network. This network structure is wrapped on the surface and pores of the cation exchange resin, significantly increasing the specific surface area and the number of functional groups of the cation exchange resin. Next, N,N-dimethylacrylamide monomers are introduced to form poly-N,N-dimethylacrylamide chains on the resin surface and in the pores through free radical polymerization. This process introduces new functional groups, such as amide groups (-CONH-) and N,N-disubstituted amino groups (-N(CH3)2). Ultimately, the modified cation exchange resin combines the original ion exchange groups (such as carboxyl groups), the hydroxyl and carboxyl groups of the calcium alginate network, and the functional groups of the poly-N,N-dimethylacrylamide chains. This multifunctional structure can simultaneously adsorb organic pollutants and metal ions through a variety of mechanisms (such as ion exchange, hydrogen bonding, chelation, hydrophobic interaction, etc.), significantly improving the treatment capacity and efficiency of cation exchange resins for complex wastewater.

[0025] The multi-level modification of the embodiment of the present invention enables the cation exchange resin to obtain a unique multifunctional structure, which can simultaneously treat organic pollutants and metal ions through multiple mechanisms of action: when treating organic pollutants, the hydroxyl, carboxyl and amide groups on the surface of the cation exchange resin enhance the affinity for polar organic matter through hydrogen bonding, the carbon-hydrogen skeleton of the poly N,N-dimethylacrylamide chain enhances the adsorption capacity for non-polar organic matter through hydrophobic action, and the three-dimensional network structure formed by calcium alginate can physically capture macromolecular organic matter; when removing metal ions, the resin performs ion exchange through the original sulfonic acid group or carboxyl group, the carboxyl and hydroxyl groups in the calcium alginate network form stable chelates with heavy metal ions, and the functional groups in N,N-dimethylacrylamide enhance the affinity for transition metal ions through weak coordination.

[0026] In some preferred embodiments, the mass ratio of the initiator, N,N-dimethylacrylamide monomer and the composite material is (0.01-0.05): (0.5-2.0): 1.

[0027] There is no need to specifically limit the concentration of the calcium chloride solution, and a person skilled in the art can select a suitable concentration for use according to the cross-linking reaction raw materials. For example, the concentration of the calcium chloride solution can be 3-7% w / v.

[0028] In some preferred embodiments, the cross-linked product is washed with deionized water and then dried at 60-80° C. for 12-24 hours to obtain a composite material.

[0029] In some preferred embodiments, the reaction product is washed alternately with deionized water and ethanol and then vacuum dried at 60-80° C. for 24-36 h.

[0030] The third technical solution adopted by the present invention is: The shale gas wastewater membrane concentrate treating agent contains the modified cation exchange resin in the first embodiment, or the modified cation exchange resin obtained by the second embodiment.

[0031] The adsorption mechanism of the modified cation exchange resin in treating shale gas wastewater membrane concentrate is as follows.

[0032] Enhanced adsorption of organic matter: (1) Hydrogen bonding: The newly added hydroxyl, carboxyl and amide groups can form hydrogen bonds with polar groups (such as -OH, -NH2, -COOH, etc.) in organic molecules, thus enhancing the affinity for polar organic matter; (2) Hydrophobic effect: The carbon-hydrogen skeleton of the poly (N,N-dimethylacrylamide) chain can produce hydrophobic interactions with non-polar organic matter, thereby improving the adsorption capacity of non-polar or weakly polar organic matter; (3) Spatial network capture: The three-dimensional network structure formed by calcium alginate can physically capture certain macromolecular organic matter, thereby increasing the removal efficiency of macromolecular organic pollutants.

[0033] Enhanced adsorption of metal ions: (1) Ion exchange: The original carboxyl groups adsorb metal cations through electrostatic action, maintaining the basic ion exchange function of the resin; (2) Chelation: The carboxyl and hydroxyl groups in the calcium alginate network can form chelates with certain metal ions, enhancing the selectivity and adsorption capacity for specific metal ions (such as heavy metals); (3) Weak coordination: The amide group and N,N-disubstituted amino group in N,N-dimethylacrylamide form weak coordination with certain metal ions, slightly enhancing the affinity for certain transition metal ions.

[0034] In some preferred embodiments, the modified cation exchange resin can also be used in conjunction with other commonly used wastewater treatment components to further improve the wastewater treatment effect in multiple aspects. For example, the shale gas wastewater membrane concentrate treatment agent is composed of the following raw materials in parts by weight: 10-20 parts of modified cation exchange resin, 5-15 parts of potassium permanganate, 10-20 parts of aminomethylated wattle bark tannin, 5-15 parts of sodium carbonate, and 15-25 parts of activated carbon.

[0035] Among them, potassium permanganate, as a pretreatment oxidant, can effectively decompose organic matter and convert part of ammonia nitrogen into nitrate nitrogen; aminomethylated wattle bark tannin removes suspended matter and colloidal particles through flocculation; sodium carbonate adjusts the pH value and reduces water hardness by forming carbonate precipitation; activated carbon uses its porous structure to further adsorb residual pollutants. This multiple guarantee mechanism ensures the stability and reliability of the treatment process, and can maintain good treatment effects even in the face of shale gas wastewater membrane concentrate with complex composition and fluctuating concentration.

[0036] The preparation method of the aminomethylated wattle bark tannin used in the present invention is a preparation method disclosed in the prior art, specifically: Dissolve the tannin from the bark of thorn tree in deionized water and adjust the pH value of the solution to 8.5-9.0. Add formaldehyde solution and diethylamine, mix well and react at 70-80°C for 3-5 hours. After the reaction is completed, cool to room temperature. Adjust the pH value of the reaction solution to 3.0-4.0, add ethanol for precipitation, filter, collect the precipitate, wash and dry.

[0037] The mass ratio of chaste tree bark tannin, formaldehyde and diethylamine can be: 1: (0.4~0.6): (0.3~0.5).

[0038] The preparation method of the shale gas wastewater membrane concentrate treatment agent is to mix the raw materials evenly, dry them to a suitable moisture content, crush them and sieve them. The specific mixing order, moisture content and mesh number of the sieve do not need to be specifically limited, and those skilled in the art can select them according to actual needs.

[0039] In order to make the technical solution of the present invention clearer, the modified cation exchange resin, its application and effects are described in detail below through a number of specific embodiments.

[0040] The test equipment and preparations of the following examples are as follows: Electronic balance (Sartorius, Germany), electric blast constant temperature dryer (Shanghai Fomar Experimental Equipment), stainless steel reactor (Shanghai Laibei), electric constant temperature water bath (Jiangsu Kedao), rotary evaporator (Shanghai Darlow Scientific Instruments), pulverizer (Shandong Tianfang Machinery), magnetic stirrer (Shanghai Meiyingpu), Soxhelt extractor (Qingdao Juchuang); chemicals and reagents were purchased from Sigma-Aldrich.

[0041] Example 1 Preparation of modified cation exchange resin: S11. D113 resin and sodium alginate were fully dispersed in deionized water to prepare a resin suspension and a sodium alginate solution; S12. The sodium alginate solution was slowly added to the resin suspension and mixed evenly, wherein the mass ratio of D113 resin to sodium alginate was 1:0.8; S13. The mixture was added dropwise to a calcium chloride solution (5% w / v) to achieve full crosslinking to form gel beads, and the beads were immersed in the calcium chloride solution for 2 h to complete crosslinking; the beads were washed with deionized water several times to remove excess calcium ions, and dried at 60° C. for 12 to 24 h to obtain a composite material; S14. Add deionized water to the dried composite material and stir evenly. Under a nitrogen atmosphere, add potassium persulfate as an initiator and add N,N-dimethylacrylamide monomer. React at 50°C for 6h. Wash the product alternately with deionized water and ethanol for several times, and vacuum dry at 60°C for 24 to obtain a modified cation exchange resin. The mass ratio of the initiator, the monomer and the composite material is 0.03:1.2:1.

[0042] Example 2 Preparation of modified cation exchange resin: S11. D113 resin and sodium alginate were fully dispersed in deionized water to prepare a resin suspension and a sodium alginate solution; S12. The sodium alginate solution was slowly added to the resin suspension and mixed evenly, wherein the mass ratio of D113 resin to sodium alginate was 1:0.2; S13. The mixture was added dropwise to a calcium chloride solution (5% w / v) to form gel beads to achieve sufficient crosslinking, and the beads were immersed in the calcium chloride solution for 2 h to complete the crosslinking; the beads were washed with deionized water several times to remove excess calcium ions, and dried at 80°C for 24 h to obtain a composite material; S14. Add deionized water to the dried composite material and stir evenly; under a nitrogen atmosphere, add potassium persulfate as an initiator, add N,N-dimethylacrylamide monomer, and continue to introduce nitrogen at 60°C for 8 hours; wash the product alternately with deionized water and ethanol for several times, and vacuum dry it at 80°C for 36 hours to obtain a modified cation exchange resin; wherein the mass ratio between the initiator, the monomer and the composite material is 0.01:0.5:1.

[0043] Example 3 Preparation of modified cation exchange resin: S11. D113 resin and sodium alginate were fully dispersed in deionized water to prepare a resin suspension and a sodium alginate solution; S12. Slowly adding the sodium alginate solution to the resin suspension, wherein the mass ratio of D113 resin to sodium alginate is 1:1; S13. The mixture was added dropwise to a calcium chloride solution (5% w / v) to form gel beads to achieve sufficient cross-linking, and the beads were immersed in the calcium chloride solution for 2 h to complete the cross-linking; the beads were washed with deionized water several times to remove excess calcium ions, and dried at 75°C for 12-24 h to obtain a composite material; S14. Add deionized water to the dried composite material and stir evenly; under a nitrogen atmosphere, add potassium persulfate as an initiator, add N,N-dimethylacrylamide monomer, and continue to introduce nitrogen at 55°C for 7 hours; wash the product alternately with deionized water and ethanol for several times, and vacuum dry it at 70°C for 30 hours to obtain a modified cation exchange resin; wherein the mass ratio between the initiator, the monomer and the composite material is 0.05:2.0:1.

[0044] Example 4 Preparation of modified cation exchange resin: S11. D113 resin and sodium alginate were fully dispersed in deionized water to prepare a resin suspension and a sodium alginate solution; S12. The sodium alginate solution is slowly added to the resin suspension, wherein the mass ratio of D113 resin to sodium alginate is 1:0.6; S13. The mixture was added dropwise to a calcium chloride solution (5% w / v) to form gel beads to achieve sufficient crosslinking, and the beads were immersed in the calcium chloride solution for 2 h to complete the crosslinking; the beads were washed with deionized water several times to remove excess calcium ions, and dried at 72°C for 20 h to obtain a composite material; S14. Add deionized water to the dried composite material and stir evenly; under a nitrogen atmosphere, add potassium persulfate as an initiator, add N,N-dimethylacrylamide monomer, and continue to introduce nitrogen at 50-60°C for 7.5 hours; after the reaction, wash the product alternately with deionized water and ethanol for several times, and vacuum dry at 78°C for 32 hours to obtain a modified cation exchange resin; wherein the mass ratio of the initiator, the monomer and the composite material is 0.03:1.25:1.

[0045] Example 5 The preparation method of the modified cation exchange resin comprises: S11. D113 resin and sodium alginate were fully dispersed in deionized water to prepare a resin suspension and a sodium alginate solution; S12. The sodium alginate solution is slowly added to the resin suspension, wherein the mass ratio of D113 resin to sodium alginate is 1:0.6; S13. The mixture was added dropwise to a calcium chloride solution (5% w / v) to form gel beads to achieve sufficient crosslinking, and the beads were immersed in the calcium chloride solution for 2 h to complete the crosslinking; the beads were washed with deionized water several times to remove excess calcium ions, and dried at 66°C for 18 h to obtain a composite material; S14. Add deionized water to the dried composite material and stir evenly; under a nitrogen atmosphere, add potassium persulfate as an initiator, add N,N-dimethylacrylamide monomer, and continue to introduce nitrogen at 52°C for 6.6 hours; after the reaction, wash the product alternately with deionized water and ethanol for several times, and vacuum dry at 73°C for 33 hours to obtain a modified cation exchange resin, wherein the mass ratio of the initiator, the monomer and the composite material is 0.02:1.8:1.

[0046] Example 6 The shale gas wastewater membrane concentrate treating agent is composed of the following raw materials in parts by weight: 12 parts of potassium permanganate, 16 parts of aminomethylated wattle bark tannin, 13 parts of sodium carbonate, 22 parts of activated carbon, and 16 parts of the modified cation exchange resin prepared in Example 1; Wherein, the preparation method of aminomethylated wattle bark tannin is: S11. The tannin powder of wattle bark was dissolved in deionized water, the pH of the solution was adjusted to 8.5-9.0 with hydrochloric acid or sodium hydroxide, 37% formaldehyde solution was added, diethylamine was slowly added dropwise, and stirred evenly; wherein the mass ratio of wattle bark tannin, formaldehyde solution, and diethylamine was 1:0.5:0.4; S12. react at 70°C for 4h, maintaining the pH between 8.5 and 9.0, and cool to room temperature after the reaction; S13. The reaction solution was adjusted to pH 3.0-4.0 with hydrochloric acid, ethanol was added, stirred for 30 min, allowed to stand for 2 h to allow the product to precipitate, and filtered to collect the precipitate; S14. Wash the precipitate with ethanol three times and dry the precipitate in a vacuum drying oven at 60°C for 12 h.

[0047] The preparation method of shale gas wastewater membrane concentrate treating agent is as follows: After fully mixing all the raw materials, dry them at 60-70℃ for 4-6 hours, or until the moisture content is less than 5%; the dried material is crushed and passed through an 80-100 mesh sieve.

[0048] Example 7 The shale gas wastewater membrane concentrate treating agent is composed of the following raw materials in parts by weight: 5 parts of potassium permanganate, 10 parts of aminomethylated wattle bark tannin, 5 parts of sodium carbonate, 15 parts of activated carbon, and 10 parts of the modified cation exchange resin prepared in Example 2.

[0049] The preparation method of aminomethylated wattle bark tannin and shale gas wastewater membrane concentrate treatment agent is shown in Example 6.

[0050] Example 8 The shale gas wastewater membrane concentrate treating agent is composed of the following raw materials in parts by weight: 15 parts of potassium permanganate, 20 parts of aminomethylated wattle bark tannin, 15 parts of sodium carbonate, 25 parts of activated carbon, and 20 parts of the modified cation exchange resin prepared in Example 3.

[0051] The preparation method of aminomethylated wattle bark tannin and shale gas wastewater membrane concentrate treatment agent is shown in Example 6.

[0052] Example 9 The shale gas wastewater membrane concentrate treating agent is composed of the following raw materials in parts by weight: 10 parts of potassium permanganate, 15 parts of aminomethylated wattle bark tannin, 10 parts of sodium carbonate, 20 parts of activated carbon, and 15 parts of modified cation exchange resin prepared in Example 4.

[0053] The preparation method of aminomethylated wattle bark tannin and shale gas wastewater membrane concentrate treatment agent is shown in Example 6.

[0054] Example 10 The shale gas wastewater membrane concentrate treating agent is composed of the following raw materials in parts by weight: 9 parts of potassium permanganate, 13 parts of aminomethylated wattle bark tannin, 8 parts of sodium carbonate, 22 parts of activated carbon, and 18 parts of modified cation exchange resin prepared in Example 5.

[0055] The preparation method of aminomethylated wattle bark tannin and shale gas wastewater membrane concentrate treatment agent is shown in Example 6.

[0056] Comparative Example 1 The treatment agent, compared with Example 6, is different only in that the modified cation exchange resin is not used, and the remaining components and preparation method are the same as those of Example 6.

[0057] Comparative Example 2 The treatment agent, compared with Example 7, is different only in that the modified cation exchange resin is omitted, and the remaining components and preparation method are the same as those of Example 7.

[0058] Comparative Example 3 The treatment agent, compared with Example 8, is different only in that the modified cation exchange resin is eliminated, and the remaining components and preparation method are the same as those of Example 8.

[0059] Comparative Example 4 The treatment agent, compared with Example 9, is different only in that the modified cation exchange resin is omitted, and the remaining components and preparation method are the same as those of Example 9.

[0060] Comparative Example 5 The treatment agent, compared with Example 10, is different only in that the modified cation exchange resin is eliminated, and the remaining components and preparation method are the same as those of Example 10.

[0061] Test example 1. Detection of the modified cation exchange resin prepared in Examples 1-5 for Ca 2+ Mg 2+ Selective adsorption capacity of ions and adsorption of organic pollutants.

[0062] (1) Ca 2+ Mg 2+ Selective adsorption experiments ① Single component adsorption: Prepare Ca2+ with concentrations of 10, 30, 50, 70, and 100 mg / L respectively. 2+ and Mg 2+ The modified cation exchange resin prepared in the example is pretreated by soaking it in a 2 mol / L HCl solution for 4-6 hours to convert the resin into H + The resin was repeatedly rinsed with deionized water until the pH of the washing solution was neutral, and then soaked in 2 mol / L NaCl solution for 4-6 hours to convert the resin into Na + Type, rinse again with deionized water until the washing solution is negative for chloride ion detection. Weigh 0.5g of pretreated resin and place it in a conical flask, add 50mL of ion solutions of different concentrations, shake at 25℃ for 24h, centrifuge and determine the ion concentration in the supernatant.

[0063] ②Two-component competitive adsorption: Preparation of Ca 2+ and Mg 2+Mixed solutions of equal concentration (50 mg / L each) were adsorbed under the same conditions as the single-component experiment, and the concentrations of the two ions in the equilibrium solution were determined.

[0064] (2) Organic pollutant adsorption experiment: prepare 100 mg / L methyl orange solution, weigh 0.5 g of the modified cation exchange resin to be tested, add 50 mL of methyl orange solution, oscillate at a constant temperature of 25 °C, take samples at different time points (0.5 h, 1 h, 2 h, 4 h, 8 h, 24 h), measure the absorbance of the solution, and obtain the methyl orange concentration at the corresponding time point based on the existing methyl orange standard curve (concentration-absorbance); calculate the methyl orange removal rate according to the following formula: Removal rate = (C0-C t ) / C0x100%, where C0 is the initial methyl orange concentration (100 mg / L), C t is the concentration of methyl orange at time t.

[0065] The test results are shown in Table 1.

[0066] 2. Comparison of the treatment effects of the treatment agent containing modified cation exchange resin in Examples 6-10 and the treatment agent not containing modified cation exchange resin in Comparative Examples 1-5 on shale gas wastewater membrane concentrate. The shale gas wastewater membrane concentrate used is from a shale gas mining site in Sichuan, and is a concentrate after ultrafiltration-nanofiltration-reverse osmosis treatment. The main physical and chemical properties of the concentrate are as follows: total dissolved solids (TDS): 25000-30000 mg / L, total hardness: 8000-10000 mg / L (calculated as CaCO3), TOC (total organic carbon): 800-1200 mg / L, barium: 150-200 mg / L, strontium: 400-600 mg / L, lead: 0.5-1.0 mg / L.

[0067] 5 g of the treatment agent of the example and the treatment agent of the comparative example were added to 500 mL of shale gas wastewater membrane concentrate, respectively, and the mixture was stirred and reacted for 2 h at 25 ° C. After standing for 30 min, the mixture was filtered and the filtrate was taken as the treated water sample, and the untreated shale gas wastewater membrane concentrate was taken as the pre-treated water sample for the following tests: (1) Determination of heavy metal concentration (barium, strontium, lead): Prepare a series of multi-element standard solutions (national standard samples) with known concentrations to establish a standard curve, inject the pretreated sample solution into the ICP-OES instrument, and determine the heavy metal concentration in the sample through instrument analysis. Heavy metal removal rate = (heavy metal concentration of water sample before treatment - heavy metal concentration of water sample after treatment) / heavy metal concentration of water sample before treatment * 100% (2) Determination of total dissolved solids (TDS): Place the cleaned evaporating dish in an oven and bake it at 105℃±2℃ for 1h, then place it in a desiccator, cool it, and weigh it. Repeat the drying and weighing of the evaporating dish until the weight is constant. Pipette 100mL of water sample filtered through a 0.45μm filter membrane and place it in an evaporating dish of constant weight. First evaporate it on a hot plate to a small volume, and then place it in a water bath to evaporate it to dryness. Place the evaporating dish in an oven and bake it at 105℃±2℃ for 1h, take out the evaporating dish, place it in a desiccator, cool it, and weigh it. Repeat the drying and weighing until the weight is constant. TDS removal rate = (TDS of water sample before treatment - TDS of water sample after treatment) / TDS of water sample before treatment * 100%.

[0068] (3) TOC determination: The shale gas membrane concentrate was filtered with a 0.45 μm filter membrane to remove suspended matter, and the original TOC was determined. The examples and comparative examples were added to the shale gas membrane concentrate, respectively, and the mixture was shaken in a constant temperature oscillator at 25°C and 150 rpm for 24 h. The TOC was determined after filtration. TDS removal rate = (TOC of water sample before treatment - TOC of water sample after treatment) / TOC of water sample before treatment * 100%.

[0069] (4) Hardness determination: dilute the wastewater, take 50 mL of the diluted sample, add 4 mL of pH = 10 ammonia buffer, add chrome black T indicator, and titrate with 0.01 mol / LEDTA standard solution until the solution changes from purple to sky blue. Hardness removal rate = (water sample hardness before treatment - water sample hardness after treatment) / water sample hardness before treatment * 100%.

[0070] The test results are shown in Table 2.

[0071] Table 1 Comparison of performance of modified cation exchange resins in Examples 1 to 5 .

[0072] Table 2 Removal of pollutants from shale gas membrane concentrate in Examples and Comparative Examples .

[0073] By analyzing the experimental data, it can be seen that the modified cation exchange resin exhibits excellent selective adsorption performance. In the single component adsorption test, the modified cation exchange resin has excellent selective adsorption performance for Ca² + and Mg² + All of them showed strong adsorption capacity, and with the increase of initial concentration, the adsorption amount also increased accordingly, showing typical isothermal adsorption characteristics. Among them, Example 2 performed the best, with a concentration of 100 mg / L for Ca² + and Mg² + The adsorption capacity of Ca² +Preferential adsorption of Ca² + / Mg² + The adsorption selectivity ratio is about 1.09, indicating that the resin has a high selectivity to Ca² + It has a slight selective preference; in the methyl orange adsorption kinetics study, all embodiments achieved a removal rate of more than 90% within 24 hours, wherein the first 4 hours were a rapid adsorption stage, 4 to 8 hours were a transition stage, and it leveled off after 8 hours. Embodiment 2 achieved the highest removal rate of 99.5% at 24 hours.

[0074] In the comparison of the treatment effects of shale gas wastewater membrane concentrate, the treatment effect of the embodiment group containing modified resin is significantly better than that of the control example, especially Example 8 performs best, with the removal rates of barium, strontium and lead reaching 94.8%, 91.9% and 96.5%, respectively, while the removal rates of TDS, TOC and hardness reach 71.8%, 87.9% and 81.5%, respectively, which are about 20 to 25 percentage points higher than that of the control example. These data fully prove that the addition of modified cation exchange resin not only provides additional adsorption sites, but also significantly improves the treatment effect through synergistic effects with other components, especially in the removal of organic matter, which shows better removal effect than inorganic pollutants, and also shows the characteristics of selective removal of heavy metals, and the removal order is lead>barium>strontium.

[0075] Finally, it should be noted that: Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A modified cation exchange resin, characterized in that: It is obtained by compounding a cation exchange resin with sodium alginate and then grafting N,N-dimethylacrylamide, and has amide groups on the surface; wherein the cation exchange resin is a weakly acidic cation exchange resin with carboxylic acid groups as exchange groups.

2. The modified cation exchange resin according to claim 1, characterized in that The mass ratio of the cation exchange resin to the sodium alginate is 1:(0.3-0.8), and the mass ratio of the N,N-dimethylacrylamide to the cation exchange resin and the sodium alginate composite material is (0.5-2.0):

1.

3. The modified cation exchange resin according to claim 1, characterized in that The concentration of the sodium alginate solution is 1.5-2.5% w / v.

4. The method for preparing a modified cation exchange resin according to any one of claims 1 to 3, characterized in that: The following steps are involved: After the fully dispersed cation exchange resin solution and the sodium alginate solution are uniformly mixed at room temperature, a calcium chloride solution is added for cross-linking, and the cross-linked product is washed and dried to obtain a composite material; In a nitrogen atmosphere, potassium persulfate is used as an initiator, N,N-dimethylacrylamide monomer is added to the composite material to react at 50-60° C. for 6-8 hours, and the reaction product is washed and dried; The cation exchange resin is a weakly acidic cation exchange resin with carboxylic acid groups as exchange groups.

5. The preparation method according to claim 2, characterized in that: The mass ratio of the initiator, N,N-dimethylacrylamide monomer and composite material is (0.01-0.05):(0.5-2.0):

1.

6. The preparation method according to claim 2, characterized in that: The concentration of the calcium chloride solution is 3-7% w / v.

7. The preparation method according to claim 2, characterized in that: The cross-linked product is washed with deionized water and then dried at 60-80° C. for 12-24 hours to obtain a composite material.

8. Shale gas wastewater membrane concentrate treatment agent, characterized in that: Contains the modified cation exchange resin as claimed in any one of claims 1 to 3, or a modified cation exchange resin obtained by the preparation method as claimed in any one of claims 4 to 7.

9. The treatment agent according to claim 8, characterized in that The invention is composed of the following raw materials in parts by weight: 10-20 parts of modified cation exchange resin, 5-15 parts of potassium permanganate, 10-20 parts of aminomethylated wattle bark tannin, 5-15 parts of sodium carbonate and 15-25 parts of activated carbon.

10. The treatment agent according to claim 9, characterized in that The preparation method of the aminomethylated wattle bark tannin is as follows: Dissolve the tannin from the bark of thorn tree in deionized water and adjust the pH value of the solution to 8.5-9.

0. Add formaldehyde solution and diethylamine, mix well and react at 70-80°C for 3-5 hours. After the reaction is completed, cool to room temperature. Adjust the pH value of the reaction solution to 3.0-4.0, add ethanol for precipitation, filter, collect the precipitate, wash and dry.